Could a Doctor Who/Sherlock Crossover Happen?

A new behind the scenes image is once again fueling speculation that Doctor Who and Sherlock could bring together two of the most iconic characters in British fiction in a crossover episode – but fans shouldn’t hold their breath for the team up.

The modern, Benedict Cumberbatch starring version of Sherlock – co-created by Doctor Who veterans Steven Moffat and Mark Gatiss – debuted to instant success in 2010 on the BBC. That was the same year Moffat took the reins of Doctor Who as showrunner, where Matt Smith’s bow tie loving take on the Time Lord was just as successful as Moffat’s take on the surly detective. Fans have long dreamed of a crossover between the two series, and have posited theories that the shows exist in the same universe through some supposed clues in each series.

Related: First Look At Jodie Whittaker’s Doctor

A newly revealed set image is only going to add to that speculation. Rachel Talalay – who has directed episodes of both series – has posted an image of outgoing Doctor Who star Peter Capaldi on the set of Sherlock:

Promised #LIWho I’d finally post this: #PCap visiting (no conspiracy) me at #Sherlock221b last year. In costume as he was working on Class that day. Now i’m done over-explaining, great moment for #WhoLock #DoctorWho pic.twitter.com/ca3aLSQIqv

— Rachel Talalay (@rtalalay) November 13, 2017

Talalay is quick to note Capaldi was just visiting the set on a day he was filming the now cancelled Doctor Who spinoff Class, and it seems highly unlikely Talalay would post the image if it was from some super secret cameo for either show.

On a more practical level, time is simply running out for any such crossover. Sherlock wrapped its fourth season last year, and while everyone involved has claimed to be open to a fifth season at some point, the busy schedules of both Cumberbatch and Martin Freeman – as well as the somewhat conclusive feeling of the fourth season – suggest that’s a long way off, if it ever comes. Moffat is also departing Doctor Who after this year’s Christmas episode, “Twice Upon A Time”, which will feature the First Doctor, portrayed by Game of Thrones veteran David Bradley, and will see Capaldi’s Twelfth Doctor regenerate into the Thirteenth Doctor, played by Broadchurch’s Jodie Whittaker, the first woman to take on the role.

The notion of a crossover between Doctor Who and Sherlock never made a tremendous amount of sense. Sherlock is a flashy, stylish show that can sometimes flirt with the trappings of action movies, but it would be quite a leap to suggest it exists in the same realm of science fiction wonder as Doctor Who. Still, for some fans, it will feel like a genuine missed opportunity to never see Sherlock and the Doctor squabble over jelly babies and nicotine patches.

Doctor Who returns with “Twice Upon A Time” on Christmas Day on BBC America.